470 Adams <& Cdker — Investigation into the Flow of Bocks. 



pressures. This resistance also may be varied as desired by 

 altering the thickness of the walls of the enclosing tube, and 

 the pressure under which the rock is being deformed can be 

 accurately measured, seeing that the whole vertical pressure is 

 brought to bear directly upon the specimen. The deforma- 

 tion may, furthermore, be carried on at temperatures 

 approaching even to incipient redness and, if required, in the 

 presence of water or steam. 



The material employed in the construction of the enclosing 

 tubes in our earlier experiments was wrought iron or a mild 

 carbon steel, but in all later work a steel containing 4*10 to 5*18 

 per cent of nickel was employed. This steel has a considerably 

 higher elastic limit than ordinary carbon steel, and our thanks 

 are due to the Bethlehem Steel Company for several consign- 

 ments of this steel which have been used in the investigation. 

 For the construction of the pistons the chromium tungsten 

 "Novo" steel was employed. This steel when heated to 

 whiteness and plunged into fish oil develops extraordinary 

 strength, a specimen having the dimensions of one of the pis- 

 tons — namely *815 inch in diameter and 1*56 inch long — when 

 tested in compression having sustained a load of 215,000 lbs., 

 equivalent to 411,880 pounds per square inch, with practically 

 no alteration of shape. The pistons of this steel may, further- 

 more, be used under the great pressures employed at tempera- 

 tures as high as 600° C. 



In order that the conditions of differential pressure may be 

 satisfactorily developed, it is necessary to make that portion of 

 the enclosing nickel-steel tube immediately surrounding the 

 central portion of the rock column thinner than it is elsewhere, 

 while leaving the portions of the tube about the ends of the 

 column thicker. This concentrates the flow or deformation of 

 the rock, giving a symmetrical bulge developed within the 

 column and between its extreme ends, and prevents the enclos- 

 ing tube from opening up under the pressure and permitting 

 the rock to force itself up between the pistons and the ends of 

 the steel tube. As the result of a long series of experiments, 

 too numerous to detail here, it was found that a tube of the 

 dimensions shown in the accompanying drawing (fig. 2) was the 

 most suitable, the thickness of the wall immediately around the 

 central part of the specimen being increased from 25 milli- 

 meters to a centimeter according to the amount of lateral 

 pressure or resistance which it is desired to develop, all the 

 other dimensions of the tube remaining the same. The pistons 

 at either end were inserted into heavy steel castings by which 

 the load was transmitted from the press. 



The rock columns upon which the experiments were carried 

 out were in most cases about 2 cm (*814: inch) in diameter and 



